Perfected device for setting synchronizing rings of a turbojet compressor

ABSTRACT

A device is dedicated to setting one or more pivoting axial flow synchronizing rings (R), comprising a drive mechanism ( 4 - 6 ) intended to rotate their rotary spindle ( 3 ) so as to set them angularly depending on angular position data supplied by a means of control. These means of control comprise firstly means of illumination ( 8, 10 ) designed to supply light to an illumination zone ( 11 ), secondly an encoder element ( 12 ) attached to the spindle of the synchronizing ring (R) in the illumination zone ( 11 ) and designed to interact with the illumination light in order to generate optical signals representing the angular position of the synchronizing ring, thirdly means ( 13   a ) designed to collect the optical signals and fourthly means of processing ( 7 ) designed to determine angular position data based on the optical signals collected.

The invention relates to the field of turbojet compressors and more particularly that of setting pivoting axial flow synchronizing rings of these compressors.

As the person skilled in the art is aware, in an axial flow turbojet the gases are compressed prior to combustion by a compressor consisting of several stages. Each stage is composed of a rotor vane wheel intended to accelerate the axial flow and a guide vane ring intended to produce the pressure increase. In order to optimise and adapt the operation of the compressor, a guide capability or limited “setting” of the aerodynamic profile, which is controlled by regulating the engine, is provided for the guide vanes (synchronizing rings).

The synchronizing rings are generally adjusted by means of a setting device comprising a drive mechanism attached to their rotary spindles (also called “vane tail spindles”). More precisely, the setting device comprises means of control designed to determine the angular position of one of the synchronizing rings and to supply the drive mechanism with instructions consisting of angular position data so that it places the synchronizing rings concerned in selected angular positions.

So that such guiding is at the optimum, it is therefore essential that the angular positioning is precisely determined. However, due to the presence of high temperatures near the synchronizing rings, the angular position is measured remotely, preferably near the control ram. This measurement is thus distorted by the presence of high vibration, thermal expansion and by play in the mechanical linkage.

Therefore, the object of the invention is to remedy all or some of the aforementioned problems.

For this purpose, a device is proposed which is dedicated to setting one or more pivoting axial flow synchronizing rings comprising a drive mechanism intended to rotate their rotary spindles in order to set them angularly depending on the position data supplied by the means of control.

This device is characterised by the fact that its means of control comprise firstly means of illumination designed to supply light to an illumination zone, secondly an encoder element attached to the spindle of the synchronizing ring in the illumination zone and designed to interact with the illumination light in order to generate optical signals representing the angular position of the synchronizing ring, thirdly means designed to collect the optical signals and fourthly means of processing designed to determine angular position data based on the optical signals collected.

Thanks to the use of optical means of detection, the angular position is measured directly on the spindle of the synchronizing ring. The measurement no longer being distorted by cinematic play, thermal expansion or vibration, its precision is therefore substantially improved.

Preferably, the encoder element is implemented in the form of an encoder wheel (portion) having at least one scale configured in order to permit the generation of variable optical signals depending on its position within the illumination zone.

In addition, the light source preferably comprises at least one optical fibre having an extremity (possibly combined with means of optical conversion) configured so as to light up the illumination zone over a surface of selected dimensions.

The invention can be implemented in two alternative embodiments, according to which the optical signals are obtained either by transmission or by reflection.

The first category (concerning transmission) consists of at least two variants.

A first variant relates to the encoder elements comprising a scale having at least one slot configured so as to transmit the light differently depending on the angular position of the encoder element. Only one slot with progressive opening or a plurality of slots of various shapes and/or spaced from one another at a variable distance are provided, for example.

A second variant relates to the encoder elements comprising a transparent scale consisting of at least one zone equipped with markings. In this case, for example, a transparent scanning reticle can be interposed between the illumination light and the encoder element and means of collection comprising photodetectors positioned facing the scale on the side opposite the illumination zone and designed to supply electrical signals representing optical signals resulting from the interaction between the illumination light, the scanning reticle and the markings.

Alternatively, the means of collection in these two variants can comprise photodetectors positioned facing the scale on the side opposite the illumination zone and designed to supply electrical signals representing optical signals transmitted to the scale. In another variant, the means of collection can comprise one or more optical fibres having one extremity (possibly combined with means of optical conversion) configured in order to collect the optical signals transmitted to the scale.

In the second category, the scale of the encoder element comprises at least one reflecting element configured so as to reflect the light differently according to the angular position of the encoder element.

In this case, firstly a transparent scanning reticle interposed between the illumination light and the encoder element and defining a transparent phase grating, secondly a reflecting element comprising markings and thirdly means of collection comprising photodetectors positioned upstream of the scanning reticle and designed to supply electrical signals representing optical signals resulting from the interaction between the illumination light, the scanning reticle and the markings can be provided, for example.

Alternatively, the means of collection can comprise at least one optical fibre having an extremity configured so as to collect the optical signals reflected to the scale.

According to another feature of the invention, one section at least of the encoder element, one section of the light source and one section at least of the means of collection are accommodated in a chamber sealed against light so that the measurements are not distorted by parasitic light.

In addition, the means of processing are preferably accommodated in a housing remote from the synchronizing ring so that they are not exposed to high temperature.

Other features and advantages of the invention will become apparent after studying the detailed description below and the accompanying drawings wherein:

FIG. 1 is a schematic, median transversal sectional view of a high pressure compressor of a turbojet,

FIG. 2 schematically illustrates in a side view an exemplary embodiment of a setting device according to the invention,

FIG. 3 is a plan view schematically illustrating the position of the encoder wheel of the setting device in FIG. 2,

FIG. 4 schematically illustrates a first exemplary embodiment of the means of detection for the setting device in a transversal sectional view following lines IV-IV in FIG. 2,

FIG. 5 schematically illustrates a second exemplary embodiment of the means of detection for the setting device in a transversal sectional view,

FIG. 6 schematically illustrates a third exemplary embodiment of the means of detection for the setting device in a transversal sectional view,

FIG. 7 is a plan view schematically illustrating an encoder wheel, which can be used in the means of detection in FIGS. 5 and 6,

FIG. 8 is a plan view schematically illustrating another encoder wheel, which can be used in the means of detection in FIGS. 5 and 6,

FIG. 9 schematically illustrates a fourth exemplary embodiment of the means of detection for the setting device in a transversal sectional view and

FIG. 10 schematically illustrates a fifth exemplary embodiment of the means of detection for the setting device in a transversal sectional view.

The accompanying drawings will not only serve to complete the invention but also possibly contribute to its definition.

The invention relates to a device for setting the pivoting axial flow synchronizing ring(s) of a turbojet compressor.

Firstly, one should refer to FIG. 1 to see in detail the location of a setting device according to the invention.

In an axial flow turbojet, a compressor, for example, a high-pressure compressor CHP as illustrated in FIG. 1 comprising several stages, is designed to compress the gases prior to combustion in the combustion chamber CC. Each stage is composed of a rotor vane wheel intended to accelerate the axial flow, the rings carrying vanes A, and a guide vane ring called synchronizing ring R intended to produce the pressure increase.

Vanes A of the rotor wheels and the guide vanes of the synchronizing rings R are accommodated in a chamber 1 delimited by a casing 2. These synchronizing rings R are mounted for rotation on the casing 2 of the compressor CHP so that they can be adjusted (or directed) into positions for optimum guiding of the axial flow by setting devices, partially illustrated. More precisely, although this does not appear on the drawing, several synchronizing rings R are generally installed between two stages of vanes A and their angular positions are controlled by the same setting device.

As this is best illustrated in FIG. 2, each synchronizing ring R comprises a rotary spindle 3, which is attached to a link 4 fitted to a drive wheel 5. Each wheel 5 is itself attached to a ram 6 having variable travel. In addition, all synchronizing rings R installed between two stages of vanes A are attached to a same wheel 5. They thus constitute stages as it were. The displacement of a wheel 5 by way of the associated ram 6 therefore causes the angular displacement of all the synchronizing rings R of a stage. The amount of travel of a ram 6 and therefore the angular adjustment position of the synchronizing rings R of a stage is determined every time by a processing module 7 depending on the required performance of the turbojet and on angular position measurements made by a means of detection on one at least of the synchronizing rings R of a stage as will be seen later.

The links 4 attached to the synchronizing rings R of a same stage, the associated wheel 5 and the ram 6 constitute the drive mechanism of a setting device, while the means of detection and the processing module 7 constitute the means of control for this setting device.

According to the invention, the means of detection of the setting device comprise firstly a light source 8, secondly means of directing the light 10 designed to supply light to an illumination zone 11, thirdly an encoder element 12 attached to the spindle 3 of one of the synchronizing rings R in the illumination zone 11 and designed to interact with the illumination light to generate optical signals representing the angular position of the synchronizing ring 5, and fourthly means 13 designed to collect the optical signals to supply these to the processing module 7.

Preferably, the light source 8 is located at a distance in a casing 9, which also accommodates the processing module 7. In addition, the means of directing the light 10 are preferably implemented in the form of one or more optical fibres.

Depending on the method of detection used, it is preferable that one section at least of the encoder element 12, the downstream extremity of the optical fibre 10 and one section at least of the means of collection 13 are accommodated in a chamber 14 sealed against light. Thus, the optical measurements are not distorted by parasitic light or by possible dust or any, in particular greasy, residues present in the turbojet.

As this is best illustrated in FIG. 3 the encoder element 12 is preferably provided in the form of an encoder wheel and more preferably still in the form of an encoder wheel portion. This comprises at least one scale 15 configured so as to permit the generation of variable optical signals depending on its position within the illumination zone 11 and therefore depending on the angular position of the synchronizing ring R to the spindle 3, which is attached to it.

Detection can be carried out either by reflection or transmission.

An exemplary embodiment configured for detection by reflection is illustrated in FIG. 4. Here the scale 15 of the encoder wheel portion 12 comprises several reflecting elements 16, the dimensions and/or patterns of which differ so that the intensity of reflected light varies according to its angular position. These 3D-type reflecting elements 16 can be implemented by selective deposition or engraving or again by photolithography or any other known technique.

The illumination light is supplied to the illumination zone 11 by the downstream extremity of the source optical fibre 10, then reflected by the reflecting elements 16 and finally collected by the upstream extremity of one or more collection optical fibres 13 a. This (these) collection optical fibre(s) then direct the reflected and collected light (or collected optical signals) to the casing 9 where they (it) undergo(es) an intensity measurement, for example using a photoelectric converter of the processing module 7. The processing module 7 is then designed in such a way as to convert the luminous intensity measured into a measurement of angular position. For this purpose, it can comprise, in a memory, a table co-relating luminous intensities to angular positions, for example. Alternatively, it can comprise a circuit or programme designed to calculate the position depending on the intensity measured.

Once the angular position has been measured, the processing module 7 can compare this to the optimum angular position, which the synchronizing rings R of the stage that it controls must assume, so that the turbojet offers selected performances. The optimum angular position can either be determined by the processing module 7 depending on external instructions, or supplied to the processing module 7 by an external control module.

If the comparison indicates that the synchronizing rings must be re-adjusted, the processing module 7 determines new angular position data, which it transmits to the ram 6 so that its travel is modulated as a consequence.

As this is schematically illustrated, the downstream extremity of the source optical fibre 10 can be configured in order to light up the illumination zone 11 over a surface of selected dimensions and the upstream extremity of the collection fibre optical 13 a can be configured in order to collect the light reflected over a surface of selected dimensions. But, alternatively or additionally, means of optical conversion, for example, a reticle or a condenser lens, can be provided between an optical fibre extremity 10, 13 a and the scale 15.

Instead of using reflecting elements in the scale 15, the latter can be treated in such a way as to present a variable reflection factor, progressing from one of its extremities to the other, for example. In a general way, any means of reflection conferring variable reflectivity on the scale 15 can be envisaged.

In addition, instead of using one or more collection optical fibres 13 a, photodetectors for example of the CCD type (for coupling charge devices) could be used.

Exemplary embodiments configured for detection by transmission are illustrated in FIGS. 5 to 10.

In the example illustrated in FIG. 5, the scale 15 of the encoder wheel portion 12 comprises at least one opening or slot 17 configured in order to let a variable quantity of light pass depending on the angular position of the encoder element. For this purpose, the slot 17 has a progressive opening as illustrated in FIG. 7, for example.

But as illustrated in FIG. 8 the scale 15 could comprise several slots 18 of variable shapes and/or spaced from one another at a variable distance. Other embodiments could also be envisaged.

To collect the light having crossed the scale 15 through its slot or slots 17 or 18, two solutions can be envisaged.

A first solution illustrated in FIG. 5 consists in placing a photoelectric conversion module 13 b (or any other means enabling photons to be converted into a measurable physical value) under the encoder wheel portion 12. This conversion module 13 b, which therefore directly collects and converts the photons, is attached to the chamber 14 by way of fixing mounts 19, for example. The result of the conversion is transmitted by a cable 20 to the processing module 7 in order to serve elaboration of the new angular position data.

A second solution illustrated in FIG. 6 consists in placing one or more collection optical fibres 13 a of the type described above with reference to FIG. 4 under the encoder wheel portion 12. The light (or optical signals collected), which has crossed the scale 15 through its slot or slots 17 or 18 (illustrated in FIGS. 7 and 8) is therefore collected by the upstream extremity of the collection optical fibre 13 a, which directs it to the casing 9 where they (it) undergo(es) an intensity measurement by way of a photoelectric converter of the processing module 7, for example. The processing module 7 is designed so as to convert the luminous intensity measured into a measurement of angular position. The result of the conversion then serves elaboration of the new angular position data.

As illustrated in FIG. 5, the slot(s) 17 or 18 formed in the scale 15 can have any type of shape and any type of spacing since they (it) enable(s) the luminous intensity collected to be varied depending on the position of the encoder wheel portion 12.

In addition, as indicated above, the downstream and upstream extremities of the source 10 and collection 13 a optical fibres can be configured in order to supply or collect the illumination or reflected light over surfaces of selected dimensions. But, alternatively or additionally, means of optical conversion such as a reticle or a condenser lens, for example, can also be provided between one optical fibre extremity 10, 13 a and the scale 15.

Instead of transmitting the illumination light through slot(s) 17 or 18 this can be transmitted via materials having variable reflectivity provided or otherwise with markings (or marks).

For example, the scale 15 of the encoder wheel portion 12 can be made of a transparent material with a variable transmission factor. For this purpose, the scale 15 can be treated so as to provide a transmission factor crossing from one of its extremities to the other. Purely, as an example, a glass-type material of variable thickness can be self-coloured up to a certain degree. In this case, collection can be effected either by means of one or more collection optical fibres 13 a or by means of a photoelectric conversion module 13 b as described above.

Alternatively, as illustrated in FIG. 9, markings (or marks) 21 acting either as local reflection means (in this case the material interposed between adjacent markings is transparent) or as local transmission means (in this case the material interposed between adjacent markings is absorbent) can be provided level with the scale 15. These markings can be formed by sand-blasting, laser processing, chemical etching or by any other known marking technique. The markings 21 can have variable shapes and/or can be spaced from one another at a variable distance.

As illustrated, collection can be effected using a photoelectric conversion module 13 b (or any other means enabling photons to be converted to a measurable physical value) placed under the encoder wheel portion 12. This conversion module 13 b, which therefore here directly collects and converts the photons is attached to the chamber 14, for example, using fixing mounts 19. The result of the conversion is transmitted by a cable 20 to the processing module 7, in order to serve elaboration of the new angular position data.

But, as in the above exemplary embodiments, the transmitted light could be collected with one or more optical fibres 13 a, possibly combined with a means of optical conversion.

Alternatively, as illustrated in FIG. 10, markings (or marks) 21 constituting a graduated wide grating (that is to say substantially above the wavelength of the light) are made level with the scale 15 and upstream of the encoder wheel portion 12, a condenser lens 22 attached to the chamber 14 by fixing mounts 23 followed by a scanning reticle 24 likewise attached to the chamber 14 by fixing mounts 25 and defining a graduated narrow grating 26 is provided. When the illumination light diffracted by the scanning reticle 24 meets the wide grating 21, the diffracted beam components practically coincide so that a kind of light projection of the graduated structure 21 is obtained downstream of the encoder wheel portion 12.

Any movement of the encoder wheel portion 12 in relation to the scanning reticle 23 causes shadow/light modulations, which can be detected by a photoelectric conversion module 13 b of the multi-element type, placed under said encoder wheel portion 12. This conversion module 13 b, which therefore directly collects and converts the photons is attached to the chamber 14 by means of fixing mounts 19, for example. The result of the conversion is transmitted by a cable 20 to the processing module 7 in order to serve elaboration of the new angular position data.

Detection of a similar type can also be envisaged in the case of operation by reflection. In this case, a scanning reticle defining a transparent phase grating, interposed between the illumination light and the encoder wheel portion 12, the scale 15 of which comprises a phase grating of the Diadur® type, and a photoelectric conversion module 13 b of the multi-element type positioned facing the scale 15 on the side opposite the illumination zone 11 and designed to supply electrical signals representing optical signals resulting from interaction between the illumination light, scanning reticle and the markings, is provided. This type of detector called “diffraction and interference detector” is also marketed by the Heidenhain Company.

In the exemplary embodiments described, the angular position measurement can be of the absolute type or the relative type. In the case of relative measurement, an absolute reference can be provided on the encoder wheel 12 as well as on the possible scanning reticles 24 and preferably a zero measurement is carried out whenever the turbojet is stopped.

The invention is not limited to the exemplary embodiments of the setting device described above purely by way of example, but it encompasses all the alternatives, which the person skilled in the art could envisage in connection with the claims below: 

1. Device for setting pivoting axial flow synchronizing ring(s) (R) for a turbojet compressor (CHP), comprising a drive mechanism (4-6) suitable for driving in rotation at least one synchronizing ring (R) spindle (3) so as to set it angularly depending on position data supplied by means of control (7-26), characterised in that said means of control comprise means of illumination (8, 10) capable of supplying light to the illumination zone (11), an encoder element (12) attached to the synchronizing ring spindle (3) in said illumination zone and designed in such a way as to interact with said light to generate optical signals representing the angular position of said synchronizing ring (R), means of collection (13) of said optical signals and means of processing (7) designed to determine angular position data based on said optical signals collected.
 2. Device according to claim 1, characterised in that said encoder element (12) is implemented in the form of at least one encoder wheel portion having at least one scale (15) configured in order to permit the generation of variable optical signals depending on its position in said illumination zone (11).
 3. Device according to any one of claim 1 and 2, characterised in that said light source (8, 10) comprises at least one optical fibre (10) having an extremity configured so as to light up said illumination zone (11) over a surface of selected dimensions.
 4. Device according to any one of claims 2 and 3, characterised in that said scale (15) comprises at least one slot (17, 18) configured so as to transmit the light differently depending on the angular position of said encoder element (12).
 5. Device according to claim 4, characterised in that said slot (17) has a progressive opening.
 6. Device according to claim 4, characterised in that said scale (15) comprises a plurality of slots (18) of various shapes and/or spaced from one another at a variable distance.
 7. Device according to any one of claims 2 and 3, characterised in that said scale is transparent and consists of at least one zone equipped with markings (21).
 8. Device according to claim 7, characterised in that it comprises a transparent scanning reticle (25) interposed between the illumination light and said encoder element (12) and in that said means of collection (13) comprise photodetectors (13 b) positioned facing said scale (15) on the side opposite said illumination zone (11) and capable of supplying electrical signals representing optical signals resulting from the interaction between the illumination light, said scanning reticle (25) and said markings (21).
 9. Device according to any one of claims 4 to 7, characterised in that said means of collection (13) comprise photodetectors (13 b) positioned facing said scale (15) on the side opposite said illumination zone (11) and capable of supplying electrical signals representing optical signals transmitted to the scale.
 10. Device according to any one of claims 4 to 7, characterised in that said means of collection (13) comprise at least one optical fibre (13 a) having an extremity configured so as to collect said optical signals transmitted to said scale (15).
 11. Device according to any one of claims 2 and 3, characterised in that said scale (15) comprises at least one reflecting element (16) configured in such a way as to reflect said light differently according to the angular position of said encoder element (12).
 12. Device according to claim 11, characterised in that it comprises a transparent scanning reticle interposed between said illumination light and said encoder element (12) and defining a transparent phase grating, whereby said reflecting element comprises markings and whereby said means of collection (13) comprise photodetectors positioned upstream of said scanning reticle and capable of supplying electrical signals representing optical signals resulting from the interaction between the illumination light, said scanning reticle and said markings.
 13. Device according to claim 11, characterised in that said means of collection (13) comprise at least one optical fibre (13 a) having an extremity configured so as to collect said optical signals reflected to said scale (15).
 14. Device according to any one of claims 1 to 13, characterised in that one section at least of the encoder element (12), one section of said light source (10) and one section at least of said means of collection (13 a, 13 b) are accommodated in a chamber (14) sealed against light.
 15. Device according to any one of claims 1 to 14, characterised in that said means of processing (7) is accommodated in a casing (9) remote from said synchronizing ring (R).
 16. Device according to any one of the above claims, characterised in that said drive mechanism (4-6) comprises a ring (5) attached by a plurality of links (4) to a plurality of synchronizing rings (R) and a ram (6) capable of adjusting said ring (5) so as to set said plurality of synchronizing rings (R) in angular positions selected according to said angular position data determined by said means of processing (7). 